1. Technical Field
The present invention relates to a bandwidth management system and method for guaranteeing quality of service (QoS) in a Voice over Internet protocol (VoIP) network.
2. Related Art
VoIP is a communication technology which provides voice telephone service, multimedia video conference service, and the like using an Internet protocol (IP), and is applicable to various devices and application services on IP networks and public switched telephone networks (PSTNs).
Methods for guaranteeing quality of service (QoS) of such Voice over Internet protocol (VOIP) services include congestion control, queue management, type of service (ToS) processing, and the like.
The QoS guaranteeing method using congestion control avoids congestion occurring due to the presence of various traffic on the network. An IP address and a port number to be processed should be first set in order to avoid congestion.
In the QoS guarantee method using queue management, packets are collected in a queue and are sent to a buffer on a transmission link using a scheduling method. Packets requiring guaranteed QoS must be put in a first queue. To this end, an IP address and port number used for a service requiring guaranteed QoS should be set in advance.
In the QoS guarantee method using ToS processing, a class of service (CoS) for each packet is determined using priority of three bits of a ToS field included in a packet sent to the network. In other words, a predefined IP address and port number should be known in order to determine the priority of three bits of the ToS field.
As described above, in the QoS guarantee methods using congestion control, queue management and ToS processing, the IP address and port number for a service requiring guaranteed QoS should be statically preset by a device manager.
Similarly, in congestion control, queue management and ToS processing used to provide guaranteed QoS in VoIP service, ranges of an IP address and port number for the VoIP service should be statically set. However, this is inconvenient because it is necessary to know port allocation policies for VoIP service of several manufacturing companies when VoIP terminals available from the manufacturing companies are used.
When the statically set IP address is used in both VoIP service and IP application service (e.g., file transfer protocol (FTP) or Telnet) as described above, QoS in the VoIP service cannot be guaranteed.
In other words, since the VoIP service and the IP application service requiring guaranteed QoS are based on one statically set IP address, congestion control, queue management, and ToS processing for the VoIP service are not performed. Therefore, QoS in the VoIP service cannot be guaranteed.
In particular, a conventional switch/router having a traffic management function uses a technique by means of which a bandwidth for strict priority queuing (SPQ) is statically set for a specific IP/port for the VoIP service in advance according to, for example, a ratio of a possible simultaneous call number to a total user number.
However, although the bandwidth is set in advance by calculating the number of simultaneous calls, the bandwidth for each VoIP call varies with codec negotiation, which is a characteristic of the VoIP call. Therefore, it is difficult to set an accurate bandwidth.
In SPQ and weight round robin (WRR) used together for real time data service and general data service, the bandwidth used by the SPQ is continuously used for the VoIP service, resulting in a limitation on effective traffic management.
When traffic bandwidth which can be processed by the switch/router is exceeded, a buffer manager's drop function is used, but bypass call service via a legacy trunk of an IP-private branch exchanger (PBX) is not considered.